1. Allan, J.A. 1992, Fortunately there are substitutes for water, otherwise our hydropolitical futures would be impossible, in ODA, Water resources ODA, London, pp.
2. The Nile;Hurst,1952
3. Long-term storage: an experimental study;Hurst,1965
4. Accounting for the environment, Finance and Development;Lutz,1991
5. Blueprint for a green economy;Pearce,1989